Oscillator circuit



Jan. 28, 1947. p 5. J. SNYDER 2,415,049

. OSCILLATOR CIRCUIT Filed May 10, 1944 L IL I l. i

J Z 3- r 9 L; y F/Gl- Patented Jan. 28, 1947 UNITED STATES PATENT OFFICE OSCILLATOR CIRCUIT Samuel J. Snyder, Washington, D. C. Application May 1!), 1944, Serial No. 534,915

8 Claims. 1

This invention relates to high frequency oscillators having anti-resonant plate circuits.

An oscillator having a tuned plate circuit will operate with increasing efiiciency as the circuit approaches exact resonance with the frequency of oscillation. But a diificulty arises: at exact resonance oscillation ceases. If the condition of exact resonance is approached too closely a variation in temperature, loading, or electrode potentials may cause oscillation to stop. In order to obtain a good margin of safety against stoppage of oscillation the common practice is to detune the plate circuit, which entails a sacrifice of efficiency.

It is an object of this invention to remove this difiiculty and permit operation of an oscillator at maximum efficiency.

A further object of my invention is to render an oscillator stable when its plate circuit is tuned to the oscillation frequency.

A further object of my invention is to improve the operation of tuned plate circuit oscillators.

The invention will be fully understood from the following description and drawing, in which:

Figure 1 is a circuit diagram of an oscillator having a resonant circuit between the control grid and anode, and Figure 2 is a diagram of a tuned grid and tuned plate circuit oscillator.

In Figure 1 is shown an oscillator having a parallel tuned circuit 5, 6 connected between the anode and cathode of an electron tube 2. A voltage source 3 is also connected between the anode and cathode through a radio frequency choke coil 9. The circuit is shown schematically and additionaI batteries, choke coils, and other conventional elements are omitted for the sake of simplicity. The control grid and cathode of tube 2 are connected through a grid leak resistor 3. Between the gride and anode is connected a second anti-resonant circuit 4, here shown as a quartz crystal. In ordinary practice the circuit 5, 6 is detuned to a frequency below the frequency of oscillation, for oscillation ceases when circuit 5, 6 is tuned to a frequency equal to or higher than the frequency of the crystal 4. To remove this undesirable necessity I add a condenser 1 between the anode and the tuned circuit 5, 6, and then tune circuit 5, 6 to the condition of minimum plate current. The function of condenser 'i is to shift the phase of the high frequency potentials on the anode with respect to the potentials on the plate side of circuit 5, 6.

In Figure 2 is shown an oscillator including an electron tube l2, a grid leak resistor IS, a quartz crystal i4 and a tuned circuit l5, IS, A voltage source 18 is connected between the anode and cathode. It is necessary in ordinary practice to detune circuitl5, It to a frequency higher than the crystal frequency. An inductance ll, which need be only of the order of a microhenry, is connected between the tuned circuit I5, I 6 and the anode of tube H2. The circuit l5, l6 may then be set in exact resonance with the crystal I4 to achieve maximum operating efiiciency and stability of oscillation. An oscillator of the type shown in Figure 2 characterized by an antiresonant grid to cathode circuit and an antiresonant anode to cathode circuit and in which the feedback takes place through the interelectrode capacity between the anode and grid is known in the art as a tuned grid-tuned plate circuit oscillator and this term is so used in the claims.

While the oscillators of Figures 1 and 2 have been illustrated as utilizing a quartz crystal as one of the tuned circuits it is obvious that any other tuned circuit or resonant element could be used. Such other elements or circuits are magnetostrictive bars, resonant transmission lines, tuning forks, resonant cavities, or ordinary inductances and capacities.

By the use of the phasing elements 7 and I1 oscillations of greater amplitude can be obtained than in customary circuits, and the oscillator may be safely loaded more heavily. Thus the output of the oscillator is effectively increased.

I claim:

1. An oscillator including an electron tube having anode, control grid and cathode electrodes, an antiresonant means connected to said grid and one of said other electrodes, an antiresonant circuit and a reactance connected in series between said cathode and another electrode, said antiresonant means and antiresonant circuit being tuned to substantially the same frequency, and said circuit and said reactance constituting a network having a single impedance peak and a reactance of the same sign at frequencies-substantially above and below that at which said impedance peak occurs.

2. An oscillator including an electron tube having anode, cathode and control grid electrodes, a frequency determining means connected between said control gid and one of said other electrodes, an antiresonant circuit and a reactance connected in series between said cathode and anode, said circuit and said reactance constituting a network having a single impedance peak and a reactance of the same sign at frequencies substantially above and below that at which said impedance peak occurs and substantially above and below the frequency of said frequency determining means.

3. A tuned grid-tuned plate circuit oscillator including an electron tube having anode, cathode and control grid electrodes, a highly selective antiresonant means connected between the control grid and cathode, means including a circuit connected between the anode and cathode having a single impedance peak at a frequency substantially equal to the frequency of oscillation and an inductive reactance throughout a frequency band including the frequency of oscillation and extending substantially above and below the frequency of said single impedance peak for maintaining said oscillator in an oscillating condition.

4. An oscillator including an electron tube having anode, cathode and control grid electrodes, antiresonant means connected between the control grid and anode, a variable antiresonant circuit connected between the cathode and anode and means for maintaining said circuit capacitive at the frequency of oscillation upon variation of said antiresonant circuit to resonance at any frequency in a band extending substantially above and below the frequency of oscillation.

5. An oscillator including an electron tube having, anode, cathode and control grid electrodes, a frequency determining means connected between the control grid and one of the other electrodes and a circuit connected between the anode and cathode, means for feeding back potentials from the anode to the control grid regeneratively when said circuit has a reactance of a given sign and degeneratively when said circuit has a reactance of the opposite sign, said circuit being antiresonant at a single frequency substantially'equal to that of the frequency determining means and having a reactance of the said given sign through a band extending substantially above and below the frequency of the frequency determining means.

6. A tuned grid-tuned plate oscillator including an electron tube having anode, cathode and control grid electrodes, antiresonant means connected between the control grid and cathode, a variable antiresonant circuit connected between the cathode and anode, and means for maintaining said circuit inductive at the frequency of oscillation upon variation of said antiresonant circuit to resonance at any frequency in a band extending substantially above and below the frequency of oscillation.

'Z. An oscillator as described in claim 6 in which said antiresonant means includes a quartz crystal.

8. An oscillator as described in claim 4 in which said antiresonant means includes a quartz crystal.

SAMUEL J. SNYDER. 

